Photothermography is an established imaging technology. In photothermography, a photothermographic element is processed in two steps. The first step involves exposing the photothermographic element to radiation on an image-wise basis to create a latent image in the photothermographic element. This step is often referred to as imaging. The second step involves heating the photothermographic element to a development temperature for a sufficient period of time to thermally develop the latent image to a visible image. This step is often referred to as developing or, simply, as processing.
Devices and methods for developing are generally known and include contacting the photothermographic element with a heated platen, drum or belt (sometimes referred to as endless belts), blowing heated air onto the photothermographic element, immersing the photothermographic element in a heated inert liquid, and exposing the element to radiant energy of a wavelength to which the element is not photosensitive.
Photothermographic elements developed using these known devices and methods often have an uneven or non-uniform image density, image distortions and/or surface abrasion defects. Non-uniform image density defects occur during the development process due to, for instance, surface variations on the heated member, the presence of foreign matter on the photothermographic element or the heated member, and insufficient allowance for outgassing of volatile materials generated during developing. Image distortions can occur due to uncontrolled dimensional changes in the base of the photothermographic element during heating and/or cooling of the photothermographic element. Surface abrasions or marring occur by dragging the photothermographic element across a stationary component in the heating device. In many applications such as text and line drawings, these defects may be acceptable. However, users of medical, industrial, graphic, and other imaging applications desire uniform and high quality images.
In particular, because many belts can have patterns or seams, the image in the photothermographic elements developed using belts can receive an unacceptable corresponding development pattern or seam mark. While drums can make efficient use of space and can have a surface free of belt patterns and seams, drums require the photothermographic element to follow a curved path which can induce curling. In addition, drums require the photothermographic element to be guided along the curved path which can cause surface marring in the photothermographic element. Furthermore, heating the photothermographic element using many known drum devices or other heating devices can create wrinkles when heating the photothermographic element.
As a result, there is a need for a thermal processor which provides uniform and high quality images. There is also a need to mate such a thermal processor with complementary devices and photothermographic elements to offer apparatus, systems, and methods which together optimize uniformity and image quality.
In addition to uniformity and image quality, there is a need for such a processor and related apparatus, systems, and methods which provide increased throughput rates. The capability to image and develop a variation of format sizes are also desirable features not currently available in high quality photothermography. Although known photothermographic apparatus, systems, and methods do have environmental advantages over wet development systems, there are still significant issues unaddressed.
One approach that has been successful is the system described in U.S. patent application Ser. No. 08/239,709 filed on Apr. 12, 1994. This system employs a series of rollers located about a heated drum. The rollers preferably have a relatively small diameter and are closely spaced to maintain uniform contact between the photothermographic element and the heated surface. The rollers also preferably have low thermal mass to minimize the time required for the system to reach a stable operating condition.
In spite of the successes of that system, the rollers do not provide uniform contact between the leading and trailing edges of the photothermographic elements due to their spacing. In addition, if the systems biasing the rollers against the drum are incorrectly adjusted, the rollers may not rotate and can scratch or mar the back surface of the photothermographic element.